<!DOCTYPE html>
<html lang="en">
<head>
    <meta charset="UTF-8">
    <meta name="viewport" content="width=device-width, initial-scale=1.0">
    <title>Document</title>
    <style>
        .box{
            width:280px;
            background-color: blue; 
            color: aliceblue;
            text-align: center;
        }

        .box:hover{
            background-color: green;
        }
        #name:focus{
            color: blue;
            background-color: red;
        }

        a:link{
            color: black;
        }
        
        a:visited{
            color:orange;
        }
        a:hover{
            color: blue;
        }
        a:active{
            color:red;
        }
    </style>
</head>
<body>
    <!--有一个div元素，默认一个背景色，鼠标移动上后变成另外一个颜色-->
    <div class="box">
        I can change my background-color
    </div>
    <form action="#">
        <label for="name">姓名:</label>
        <input type="text" id="name" name="name">
    </form>
    <a href="https:www.baidu.com">百度</a>
</body>
</html>